Feedback control method and apparatus in closed-loop transmit diversity

Abstract

Disclosed is a feedback control method in closed-loop transmit diversity in which feedback information representing amounts of amplitude and phase control is transmitted from a mobile station to a radio base station. The mobile station receives downlink pilot signals, which are transmitted by a handover-destination base station, during handover control, calculates feedback information, which represents amounts of amplitude and phase and phase control transmitted to the handover-destination base station, beforehand based upon the pilot signals received, and transmits the feedback information to the handover-destination base station before completion of base-station changeover by handover.

1. A feedback control method in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, comprising:
 receiving downlink pilot signals, which are transmitted by a handover-destination base station, during handover control; 
 calculating feedback information, which represents an amount of phase control transmitted to said handover-destination base station, beforehand based upon the pilot signals received during handover control; 
 transmitting said feedback information to the handover-destination base station before completion of base-station changeover by handover; and 
 after completion of the base-station changeover by handover, immediately subjecting a downlink transmit data signal to phase control at said handover-destination base station using said feedback information. 
 
     
     
       2. A feedback control method according to  claim 1 , further comprising:
 providing the radio base station with a plurality of antenna elements; 
 at said base station, subjecting the same transmit data signal to different phase control based upon the feedback information from the mobile station; 
 multiplexing each of pilot signals onto respective one of the transmit data signals that have been subjected to said different phase control and transmitting each of the resultant signals using respective one of the antennas; and 
 on the side of the mobile station, calculating the feedback information using downlink pilot signals, multiplexing said feedback information onto an uplink channel signal and transmitting the resultant signal to the side of the base station before completion of base-station changeover by handover. 
 
     
     
       3. A feedback control method in closed-loop transmit diversity according to  claim 1 , wherein the feedback information is transmitted to the handover-destination base station in advance of completion of base-station changeover by handover, taking feedback-control delay time into consideration. 
     
     
       4. A feedback control method in closed-loop transmit diversity according to  claim 2 , wherein each antenna element of the base station is constituted by an antenna array for beam forming. 
     
     
       5. A feedback control method in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, comprising:
 receiving each of downlink pilot signals, which are transmitted by a plurality of base stations, during soft handover control; 
 calculating feedback information, which represents an amount of phase control transmitted to each base station, based upon each of the pilot signals received during soft handover control; 
 transmitting said feedback information to a handover-destination base station before completion of base-station changeover by soft handover; and 
 after completion of the base-station changeover by handover, immediately subjecting a downlink transmit data signal to phase control at said handover-destination base station using said feedback information. 
 
     
     
       6. A feedback control method according to  claim 5 , further comprising:
 providing each of the radio base stations with a plurality of antenna elements; 
 at each base station, subjecting an identical transmit data signal to different phase control based upon the feedback information from the mobile station; 
 multiplexing each of pilot signals onto respective one of the transmit data signals that have been subjected to said different phase control and transmitting each of the resultant signals using respective one of the antennas; and 
 on the side of the mobile station, calculating the feedback information using downlink pilot signals, multiplexing said feedback information onto an uplink channel signal and transmitting the resultant signal to the side of the base station before completion of base-station changeover by soft handover. 
 
     
     
       7. A feedback control method in closed-loop transmit diversity according to  claim 5 , wherein the feedback information is transmitted to the handover-destination base station in advance of completion of base-station changeover by soft handover, taking feedback-control delay time into consideration. 
     
     
       8. A feedback control method in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, comprising:
 receiving each of downlink pilot signals, which are transmitted by a plurality of base stations, during soft handover control; 
 calculating feedback information, which represents an amount of phase control transmitted to each base station, based upon each of the pilot signals received, and calculating receive power from each base station based upon received pilot signals during soft handover control; 
 deciding that a base station exhibiting maximum receive power is a changeover-destination base station; 
 transmitting an ID of said changeover-destination base station and the feedback information, which is sent to said changeover-destination base station, to the base stations simultaneously; 
 after completion of the base-station changeover by soft handover, immediately subjecting a downlink transmit signal to phase control at said changeover-destination base station using said feedback information. 
 
     
     
       9. A feedback apparatus of a mobile station in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, said feedback apparatus comprising:
 a receiver for receiving downlink pilot signals, which are transmitted by a handover-destination base station during handover control; 
 a control unit for controlling calculation of feedback information, which represents an amount of phase control transmitted to the handover-destination base station, beforehand based upon the pilot signals received, and controlling transmission of said feedback information to the handover-destination base station before completion of base station changeover by handover; 
 a control-amount calculation unit for calculating said feedback information beforehand based upon the pilot signals received; and 
 a transmitter for transmitting said feedback information to the handover-destination base station before completion of base-station changeover by handover, 
 wherein after completion of the base-station changeover by handover, said handover-destination base station immediately subjects a downlink transmit data signal to phase control using said feedback information. 
 
     
     
       10. A feedback apparatus of a mobile station in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, said feedback apparatus comprising:
 a receiver for receiving each of downlink pilot signals, which are transmitted by a plurality of base stations, during soft handover control; 
 a control unit for controlling calculation of feedback information, which represents an amount of phase control transmitted to each base station, beforehand and controlling transmission of said feedback information to a handover-destination base station before completion of base station changeover by soft handover; 
 a control-amount calculation unit for calculating said feedback information, based upon each of the pilot signals received; and 
 a transmitter for transmitting said feedback information to the handover-destination base station before completion of base-station changeover by soft handover, 
 wherein after completion of the base-station changeover by soft handover, said handover-destination base station immediately subjects a downlink transmit data signal to phase control using said feedback information. 
 
     
     
       11. A feedback apparatus of a mobile station in closed-loop transmit diversity in which feedback information representing at least an amount of phase control is transmitted from a mobile station to a radio base station, said feedback apparatus comprising:
 a receiver for receiving each of downlink pilot signals, which are transmitted by a plurality of base stations, during soft handover control; 
 a control-amount calculation unit for calculating feedback information, which represents an amount of phase control transmitted to each base station, based upon each of the pilot signals received; 
 a receive-power calculation unit for calculating receive power from each base station based upon received pilot signals; 
 a changeover-destination base station decision unit for deciding that a base station exhibiting maximum receive power is a changeover-destination base station; 
 a transmitter for transmitting an ID of said changeover-destination base station and the feedback information, which is sent to said changeover-destination base station, to the base stations simultaneously; and 
 a control unit for controlling the control amount calculation unit to calculate said feedback information, which represents an amount of phase control transmitted to each base station, beforehand and controlling the transmitter to transmit said ID of said changeover-destination base station and the feedback information, which is sent to said changeover-destination base station, to the base stations simultaneously, 
 wherein after completion of the base-station changeover by soft handover, said changeover-destination base station immediately subjects a downlink transmit data signal to phase control using said feedback information.